The Rigsthula, preserved among the Poetic Edda's poems, tells a story not otherwise told here: that Heimdall, walking the earth under the name Rig, is the mythic father of human social rank itself. Rig travels on foot to three households in turn, each poorer or grander than the last, and stays three nights in each, sleeping between the man and woman of the house. Nine months after his visit to the first, poorest household, a son is born there, dark haired and coarse handed, who is given the name Thrall and becomes ancestor to the servant and laboring class. The second household, more comfortable, produces a ruddy, sturdy son named Karl, ancestor to the free farmers and craftsmen. The third and grandest household produces a fair haired son named Jarl, and the poem follows Jarl further than the other two, describing him growing skilled in war, the hunt and swimming, until Rig himself returns to teach his favored son the runes and acknowledge him by name as his own, setting Jarl above his brothers as the ancestor of Norse nobility. A watchman who stands permanently at the edge of the gods' own hall, in this account, is also the figure Norse tradition credited with walking among mortals and setting the shape of their society from the ground up.